Neurons are highly compartmentalized cells that require unique mechanisms for trafficking proteins and organelles to their specific compartments. Mitochondria are vital organelles that regulate the levels of ATP, calcium homeostasis and apoptosis. Many neurodegenerative diseases including ALS, Huntington's, Parkinson's and Alzhemier's show a disruption of mitochondrial transport in the axon suggesting that mitochondrial localization and function must be highly regulated for the neuron to function properly. This study will develop an in vivo method for the live imaging of sparsely labeled layer 2/3 cortical neurons via 2-photon microscopy. This method will then be used to quantitate mitochondrial dynamics and presynaptic capture along axons in vivo. The role of neuronal activity will also be interrogated to determine the effect it has on mitochondrial dynamics, presynaptic capture and function. Finally, this study will develop a method for the unbiased identification of proteins unique or abundant in axonal mitochondria as compared to somato-dendritic mitochondria. The results of this study will provide new insights into the in vivo mechanisms of mitochondrial dynamics and how activity regulates their presynaptic capture and function.